Proteomic analysis of calcified abdominal and thoracic aortic aneurysms

Aortic aneurysm is a complex multifactorial disease with genetic and environmental risk factors. It is often accompanied by aortic calcification. Here, to uncover proteins that are significantly changed in calcified abdominal aortic aneurysms (CAAs) and calcified thoracic aortic aneurysms (CTAs) compared with those in adjacent normal aorta tissues, comprehensive analysis of differentially expressed proteins in their tissues was performed by a quantitative proteomic approach with iTRAQ labeling in combination with nanoLC-MALDI-TOF/TOF-MS/MS followed by ProteinPilot analysis. The proteomic analysis revealed 138 and 134 proteins differentially expressed in CAAs and CTAs in contrast to neighboring normal aorta tissues with high confidence, respectively. Significantly increased expression (≥1.3-fold) was found in 41 and 28 proteins, whereas decreased expression (<0.77-fold) was found in 4 and 60 proteins in CAAs and CTAs, respectively. Among them, we identified already known proteins involved in aneurysm formation and vascular calcification, such as type I and III collagen, matrix Gla protein, and α-2-HS-glycoprotein in CAAs and fibrinogen α, β and γ chains and α-2-HS-glycoprotein in CTAs with increased expression and mimecan in CAAs and fibulin-5 in CTAs with decreased expression. Based on the Panther pathway and Genesis clustering analyses, some of the proteins could be linked to corresponding biochemical pathways, such as the integrin signaling pathway with increased expression in CAAs, the blood coagulation pathway with increased expression in CTAs, and the inflammation mediated by chemokine and cytokine signaling pathway and the glycolysis pathway with decreased expression in CTAs. Interestingly, it was found by clustering analysis that samples from CAAs of patients with both CAAs and CTAs were clustered outside the samples of patients with CAAs and were clustered with samples of patients with CTAs. Our results provide a comprehensive patient-based proteomic analysis for the identification of potential biomarkers for CAAs and CTAs.